Nice work! I remembered your name/icon, this is a lot of progress from the duck jam! The "laser corpse" actually works pretty nicely to help figure out how to adjust (at least initially unless too many get shot off). I had a lot of similar feedback to others so here are some suggestions on how you might fix some.
I think actually making the laser speed user-controlled would be good; sometimes it's nice to make sense of the path, sometimes you want it to go fast, just let the users decide for themselves.
When the click starts, you might save the offset from the mirrors position and add so the mirror doesn't jump around.
Even if you don't do a laser sight in the game, I'd definitely make one for debugging, you can actually make a node (inherit from CanvasItem) and override `_draw()` to do custom things and call special functions like `draw_polyline() . Building off this, I think I'd generally want "instant fire" mode, that maybe left a scorch mark at the end to help judge how off I was.
From another comment, I'm not entirely sure how you're figuring out reflection, but the way I did it was using raycasts: `ray.global_transform.x.bounce( ray.get_collision_normal() )`, this works because I set the raycast x=1000, y=0, godotneers youtube recently did a great vid on transforms that explain what all that means.
Again, really great work, looking forward to update. Hopefully this helps you get a ... mirror polish.